Automatic RF output power-limiting amplifier with dynamic feedback

Abstract

An amplifier includes a gain stage having a gain stage input and a gain stage output and an impedance matching circuit connected to the gain stage output, the impedance matching circuit including an input and an output. The amplifier also includes a coupling circuit connected to the input of the impedance matching circuit and a shorting circuit connected to the output of the impedance matching circuit. The coupling circuit provides a voltage to the shorting circuit that causes the shorting circuit create a short to ground through a reflecting capacitor which causes a reflection to be provided to the output of the impedance matching circuit and that is transmitted to the coupling circuit to increase the voltage provided to the shorting circuit by the coupling circuit.

What is claimed is: 
     
         1 . An amplifier comprising:
 a gain stage having a gain stage input and a gain stage output;   an impedance matching circuit connected to the gain stage output, the impedance matching circuit including an input and an output;   a coupling circuit connected to the input of the impedance matching circuit; and   a shorting circuit connected to the output of the impedance matching circuit;   wherein the coupling circuit provides a voltage to the shorting circuit that causes the shorting circuit to create a short to ground through a reflecting capacitor which causes a reflection to be provided to the output of the impedance matching circuit and that is transmitted to the coupling circuit to increase the voltage provided to the shorting circuit by the coupling circuit.   
     
     
         2 . The amplifier of  claim 1 , wherein the coupling circuit includes a coupling capacitor connected to the gain stage output. 
     
     
         3 . The amplifier of  claim 2 , wherein the coupling circuit includes a storage capacitor connected between the coupling capacitor and ground that stores power coupled from the output of the gain stage output by the coupling capacitor. 
     
     
         4 . The amplifier of  claim 3 , wherein the coupling circuit further comprises a diode connected between the coupling capacitor the storage capacitor such that charge flows from the coupling capacitor to the storage capacitor. 
     
     
         5 . The amplifier of  claim 4 , further comprising a first resistor connected between an output of the coupling circuit and the shorting circuit. 
     
     
         6 . The amplifier of  claim 4 , wherein the shorting circuit includes a transistor having a gate connected to an output of the coupling circuit such that the voltage provided by the shorting circuit controls operation of the transistor. 
     
     
         7 . The amplifier of  claim 6 , wherein the the reflecting capacitor is connected to the transistor and the transistor controls if power is provided to the reflecting capacitor. 
     
     
         8 . The amplifier of  claim 6 , wherein the reflecting capacitor is connected between the output of the impedance matching circuit and the transistor. 
     
     
         9 . The amplifier of  claim 6 , wherein the transistor is connected between the output of the impedance matching circuit and the reflecting capacitor. 
     
     
         10 . The amplifier of  claim 6 , wherein the coupling circuit further includes a second resistor connected in parallel with the diode. 
     
     
         11 . The amplifier of  claim 6 , wherein the coupling circuit further includes a third resistor connected in parallel with the storage capacitor. 
     
     
         12 . The amplifier of  claim 1 , wherein the coupling circuit operates as a charge pump. 
     
     
         13 . The amplifier of  claim 1 , wherein the impedance matching circuit transforms a short circuit created through the reflecting capacitor into an open circuit at the input.